N-3 polyunsaturated fatty acids (PUFAs) exert immunosuppressive effects and have great potential as nutraceuticals for the treatment of inflammation associated disorders. A major limitation of using these fatty acids in the clinic as immunosuppressants is a poor understanding of their targets and molecular mechanisms. In vitro studies from our laboratory show that n-3 PUFAs suppress the function of antigen presenting cells (APCs) through the major histocompatibility complex (MHC) class I antigen presentation pathway by modifying the biophysical organization of the APC plasma membrane. The goal of this proposal is to test our in vitro model at the whole animal level in order to establish biological relevance. Our central hypothesis is that n-3 PUFA acyl chains form organizationally distinct nanometer scale plasma membrane domains that disrupt the distribution of sphingolipid/cholesterol-rich lipid rafts and thereby disrupt the lateral organization of MHC class I molecules (Specific Aim 1). By altering MHC class I lateral organization, the APC does not form a stable immunological synapse, which suppresses the ability of the APC to efficiently activate a na[unreadable]ve CD8+ T cell (Specific Aim 2). We will also test our hypothesis with the MHC class II pathway to address whether the effects of n-3 PUFAs on APC plasma membrane organization and subsequent function are limited to one pathway of antigen presentation or if the effects can be generalized to another pathway (Specific Aim 2). To test our model, we will rely on a combination of biophysical microscopies and functional immunological assays. If our hypothesis is correct, we will establish that dietary n-3 PUFAs can disrupt lipid and protein membrane organization on a nanometer scale and thereby suppress APC function. Given that APCs have a role in the removal of autoantigens and infectious agents, the studies proposed here will assist in the development of n-3 PUFAs as nutraceuticals for the treatment of inflammatory and autoimmune disorders, while minimizing their potential drawbacks. PUBLIC HEALTH RELEVANCE: N-3 polyunsaturated fatty acids (PUFAs) have potential therapeutic value for the treatment of inflammation associated disorders;however, their targets and mechanisms are poorly understood. This grant proposal aims to test a new model on how n-3 PUFAs modify the function of specific immune cells. Data generated from this proposal will contribute to the development n-3 PUFAs as nutraceuticals.